Stable salicylate composition



Patented June 17,.. 1930 UNITED STATES MYEB OOPLANS, OF LONDON, ENGLAND smnnn sALIcYnA'rE comrosrrrroiw Ho Drawing. Application filed December 20, 2928, Serial No. 37,477, and in Great Britain January 12, 1828.

I have invented a new composition of matter which consists essentially of a nonpoisonous alkaline earth salt of acetyl-salicylic acid mixed with the chloride of the non-poisonous alkaline earth.

Compared with free acetyl-salicylic acid (aspirin) the salts of this acid with alkalies or alkaline earths possess consider able advantages as medicinal agents, by rea- 1 son of their ready solubility in water, their diminished taste, and their more rapid absorption. Up to the present, however, the preparation and employment of these salts has been greatly limited by the extreme instability which they exhibit. The calcium salt, for example, even when obtained in a ure state, rapidly decomposes on keeping, ibrming calcium salicylate and free acetic acid, so that in the course of a few months or even weeks it may become unusable or a danger to health if administered.

It is the object of the present invention to overcome'this difficulty and thus enable preparations to be marketed possessing a de ree of'stability which will allow of their sa e employment. A further object of the invention is to aiiord an economical method of preparing such salts, namely, the calcium and magnesium salts, in which hydrolysis of the material is avoided during the preparation and a good yield'of the product obtained without the necessity of employing expensive solvents.

My experiments have demonstrated that the abovementioned decomposition, to which salts of acetyl-salicylic acid are liable, is promoted by the presence of water, either water of crystallization or water otherwise held or absorbed by the crystals, which by bringing the salt into solution slowly eflects hydrolysis of the product.

It might have been thought that the addition to the salts of acetyl-salicylic acid of a highly hygroscopic substance like calcium chloride would promptly make the material wet and promote its decomposition. I have found that this is not the case, but that my new composition of matter is very much more stable than the salts of acetyl-salicylic 50 acid without the admixture of the chlorides.

It appears that such salts, by engaging the water present, prevent any de ree of solu-. tion of the acetyl-salicylate, an thus hinder or prevent decompositlon. Moreover, by effecting the preparation of the acetyl-salicylate in the presence of one of the said salts, the isolation of the acetyl-salicylate in good yield and free from decomposition products is greatly facilitated.

In the preparation of calcium acetylsalicylate, the most suitable inorganic salt for these purposes is calcium chloride, by

the calcium or magnesium chloride may either be incorporated with the ready prepared acetyl-salicylate or during the prep aration of the latter. The following examples illustrate the manner of carrying out my invention, but the invention is not limited to the exact proportions or procedure here given. The products are colourless crystalline powders, easily soluble in water, and having comparatively little taste.

Example 1.To a paste consisting of 100 parts by weight of pure freshly prepared calcium acetyl-salicylate and 100 parts by weight of water, there is-slowly added 25 I parts b weight of anh drous calcium chloride, t e mixture bemg kept cold and kneaded together. When the calcium .chloride has entirely dissolved, the whole is dried at a temperature of about 40 C. and then ground to powder.

Example 2.90 parts by weight of finely ground acetyl-salicylic acid is suspended in 400 parts by volume of a solution of calcium chloride containing 25 g. of OaCl, per 100 c. c. 25 parts by weight of precipitated calcium carbonate (1' 0) or 18.5 parts by weight of calcium hydrate are a ded and the mixture is stirred in the cold or with ver gentle warming until the evolution of car on dioxide'has ceased. The calcium acet l-salicylate which has crystallized out is tered ofi upon a vacuum-fi ter or centrifugator, well pressed, and dried without washing at about 40 C. The product retains from 10 to 15% calcium chloride.

Example 51-90 parts by weight of very finel ground acetyl-salicylic acid is suspen ed in 100 parts by volume of a solution of calcium chloride containing 40 CaCl per 100 c. c. and gently warmed an stirred to obtain a uniform paste. This is then mixed with a suspension of 26 parts by weight of precipitated calcium carbonate (100%) in 300 parts by olume of calcium chloride solution of the above strength. The mixture is stirred and warmed gently, not above C. until the frothing has entirely ceased. This requires 2 or 3 hours. The calcium acet l-salicylate which has then separated is fi ltered off on the vacuum-filter,

- washed with 200 parts by weight of calcium washing with magnesium chloride solution,-

chloride solution of the above strength, and well pressed. The product is dried in a vacuum oven at a temperature of about 60 C. It contains from 5 to 7% calcium chlo ride.

Example 4.180 parts by weight of finely ground acetyl-salicylic acid is suspended in 600 parts by volume of a solution of calcium chloride containing 25 g. CaCl per 100' c. c. The cold mixture is kept rapi ly stirred whilst parts by weight of sodium bicarbonate is slowly added. When the evolution of carbon dioxide has ceased, the paste is filtered upon a vacuum filter, well pressed, and drie at 40 C. If it is desired to wash the product, this should be done with calcium chloride, not with water. The product is calcium acetyl-salicylate with a little calcium chloride.

Ewample 5.A mixture of parts-by weight of finely ground acetyl-salicylic acid is lncorporated in an edge-runner with 1000 parts by volume of magnesium chloride solution containing 40 g. MgCl per 100 c. c. and to this is added 46 parts by weight of magnesium carbonate levis (3 gCO Mg(OH) 3H O). The mixture is warmed gently until reaction is complete. The magnesium acetyl-salicylate is then filtered ofl', freed from mother-liquor by and dried carefully at 60 C.

What I claim and desire to secure by Letters Patent is 1. As a new composition of matter, a nonpoisonous alkaline earth salt of acetyl-salicylic acid mixed with a small quantity of the chloride of the non-poisonous alkaline earth.

2. As a new composition of matter, a medicinal reparation consisting of calcium acetyl-sa icylate, containing a small quantity of calcium chloride.-

3. The method of stabilizing solid calcium and magnesium acetyl-salicylates, by incorporating therewith small quantities of the chlorides of. calcium and magnesium.

4. The preparation of calcium acetylsalicylate containing small quantities of calcium chloride by causing acetyl-salicylic acid to react with calcium carbonate or calcium hydrate in the presence of a strong solution of calcium chloride and pressing off the product with removal of a portion only of the calcium chloride.

- 5. The preparation of a non-poisonous alkaline earth salt of acetyl-salicylic acid containing small quantities of a chloride of the said alkaline earth b causing acetyl-salicylic acid to react wit the carbonate or hydrate of said alkaline earth in the presence of a strong solution of the chloride of said alkaline earth and pressing off the product with removal of a portion only of the said chloride.

6. The preparation of non-poisonous alkaline earth acetyl salicylates containing small quantities of non-poisonous alkalineearth chlorides by causing acetyl-salicylic acid to react with non-poisonous alkaline earth carbonates in the presence of a strong solution of non-poisonous alkaline earth chlorides and separating the product with removal of a portion only of the alkalineearth chlorides.

In testimony whereof I aflix my signature.

MYER COPLANS. 

